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Migrating email accounts to FastMail

I keep planning to add this to the documentation, but I thought I'd write it up quickly as a blog post.

One recurring question we have get is people asking the best way of migrating accounts from an existing system to a new FastMail family/business package. Basically there's two main approaches:

All in one go

One account at a time

The documentation below helps explain these two approaches, and the other tools we provide to help you migrate accounts from other services to FastMail.

All in one go

The main advantage of this process is that it's a decisive cut-over from the old system to the new. The disadvantage is that after you change the MX records, you have to run the IMAP Migrate for all users so they get their existing email at FastMail, and if any users use email software (eg Outlook Express, Thunderbird, etc), you have to update all of them to use the new server names at once after the MX change over.

Signup your family/business at FastMail (just follow the links near
the bottom of the login screen at http://www.fastmail.fm)

During the signup, add any domains you want to use, even if they're
currently hosted externally

Create the accounts you want (eg john@example.com, etc) and any
aliases you want

When all the accounts & aliases are setup and ready, switch the MX
records for your domain to point to us. Depending on the TTL of the
domain, after about an hour all new email should be delivered to
FastMail servers, and thus the FastMail accounts

Use the Options -> IMAP Migrate feature for each user to
copy email from the old accounts to the new accounts

One account at a time

The main advantage of this process is that it allows you to move one account at a time from the old system to FastMail giving you time to gradually move users. For each user, you can migrate them, update that users email software to access our servers, and generally ensure that each transfer is smooth and complete, before moving onto the next user.

Signup your family/business at FastMail (just follow the links near the bottom of the login screen at http://www.fastmail.fm)

During the signup, add any domains you want to use, even if they're currently hosted externally

At your existing site, setup a forward to forward all email arriving
at the old site for john@example.com to us via one of our
forwarding tunnel addresses (see below). Once you've done that, any
new email that arrives at the old site will be forwarded to us

Login to the john@example.com account at FastMail, and useOptions -> IMAP Migrate to copy all the email from your old
server to us

At this point all old mail will have been copied to us, and any new
email will be forwarded to us

Update the users email software to connect to our servers and/or
tell them to login to are webmail interface

Once you've done all accounts, change the MX records to point to us, completely removing the old site from handling your email. Everything moved over, no downtime, no lost email, no interruption

Forwarding Tunnel

The forwarding tunnel (previously documented here) allows you to forward email from an existing service to an account with the same name at FastMail. eg Say you have the account john@example.com at an existing service. You want to create your
account as john@example.com at FastMail, but how do you forward from the old john@example.com account to the FastMail john@example.com account while the DNS still points to the old server? This is what the forwarding tunnel solves.

It basically gives an extended email address syntax that you can forward email to, which will deliver to our servers, and then decode to the account name. There are 3 encoding options because some providers are limited by what characters you can put in an email address to forward to.

To forward email to the FastMail account john@example.com, you can forward to any of these 3 addresses:

IMAP Migrate

The Options -> IMAP Migrate feature allows you to migrate email from an existing IMAP server to FastMail. During the migration, it will attempt to preserve the existing folder structure, emails and email state (eg seen or unseen) from the existing server. The migration may take some time depending on the size of the account it's migrating. The migration will run in the background, and will email you when it's completed with a status report of what it did and if it encountered any problems. In general if it does encounter problems, it will try several times on a folder before giving up and moving to the next folder.

The most common reason for problems are:

Buggy IMAP servers - we've seen buggy IMAP servers that just "crash"
and close the connection when trying to retrieve some emails.
Unfortunately when this happens there's not much we can do to
retrieve the problem emails

Hidden rate limits - this seems to be a particular problem with
large gmail accounts. Technically google never advertise that gmail
accounts have any limits, but it seems if you retrieve a large
number of emails from a gmail account in a short time, it will just
close the connection to the other side with no explanation or
warning. The IMAP Migrate feature gives you the option to migrate
individual folders at a time, so if you do have disconnect problems,
you can migrate problem folders individually